drupal/core/modules/image/config/install/image.style.thumbnail.yml

name: thumbnail
label: 'Thumbnail (100x100)'
effects:
  1cfec298-8620-4749-b100-ccb6c4500779:
    id: image_scale
    data:
      width: 100
      height: 100
      upscale: true
    weight: 0
    uuid: 1cfec298-8620-4749-b100-ccb6c4500779
langcode: en